Green’s Dictionary of Slang

1. openly, undisguisedly, intensely.

[1894		Truth (Sydney) 25 Nov. 7/6: Drunk and disorderly, makin’ use of ondacent and abusive language [...] behavin ’righteously’ and tarin’ me uniform].
1944		D. Burley Orig. Hbk of Harlem Jive 25: Now, I’ve never been lit up and righteously high, / When my boots were not on, and my thinkbox not spry.
1967		M. Braly On the Yard (2002) 330: You’re getting righteously hooked on that broad, aren’t you, Chilly?
1975		J. Carr Bad (1995) 73: We ran smack into Pierce, who was righteously pissed off that we had been avoiding him.
1980		E. Folb Runnin’ Down Some Lines 89: Be righteously eyeballin’ each other.
1981		J. Ellroy Brown’s Requiem 108: Somebody righteously thrashed old Omar’s pad the other day.

2. honestly, dependably, with integrity.

1964		A. Bennett God the Stonebreaker 9: If you and the rest live righteously, there will be no work for the police.
1968		N. Giovanni ‘A Revolutionary Tale’ in King Black Short Story Anthol. (1972) 31: That’s when you come out of your thing so righteously and whip it on her so beautifully.
1977		E. Bunker Animal Factory 124: You don’t know who’s faking and who’s righteously a bad motherfucker.
1983		G. Tate ‘Santana’ in Flyboy in the Buttermilk (1992) 92: Do it righteously jam Homeboy?
2001		(con. 1975–6) E. Little Steel Toes 111: ‘Why is this woman going to help us out?’ ‘Because she’s righteously my friend.’.
2013		T. Robinson Hard Bounce [ebook] I almost called him sir. Junior would have righteously kicked my ass later.